Merge pull request #28 from kpenfound/flowchart_arrangements

Author: AlexanderGrooff

cmd/direction.go

@@ -58,9 +58,21 @@ func determineStartAndEndDir(e *edge) (direction, direction, direction, directio
 	}
 	d := determineDirection(genericCoord(*e.from.gridCoord), genericCoord(*e.to.gridCoord))
 	var preferredDir, preferredOppositeDir, alternativeDir, alternativeOppositeDir direction
+
+	// Check if this is a backwards flowing edge
+	isBackwards := false
+	if graphDirection == "LR" {
+		// In LR mode, backwards flow is when edge goes from right to left (Left direction)
+		isBackwards = (d == Left || d == UpperLeft || d == LowerLeft)
+	} else { // TD mode
+		// In TD mode, backwards flow is when edge goes from bottom to top (Up direction)
+		isBackwards = (d == Up || d == UpperLeft || d == UpperRight)
+	}
+
 	// LR: prefer vertical over horizontal
 	// TD: prefer horizontal over vertical
 	// TODO: This causes some squirmy lines if the corner spot is already occupied.
+	// For backwards edges, use special start positions: Down in LR mode, Right in TD mode
 	switch d {
 	case LowerRight:
 		if graphDirection == "LR" {
@@ -88,8 +100,9 @@ func determineStartAndEndDir(e *edge) (direction, direction, direction, directio
 		}
 	case LowerLeft:
 		if graphDirection == "LR" {
+			// Backwards flow in LR mode - start from Down, arrive at Down
 			preferredDir = Down
-			preferredOppositeDir = Right
+			preferredOppositeDir = Down // Edge goes to bottom of destination
 			alternativeDir = Left
 			alternativeOppositeDir = Up
 		} else {
@@ -100,22 +113,46 @@ func determineStartAndEndDir(e *edge) (direction, direction, direction, directio
 		}
 	case UpperLeft:
 		if graphDirection == "LR" {
-			preferredDir = Up
-			preferredOppositeDir = Right
+			// Backwards flow in LR mode - start from Down, arrive at Down
+			preferredDir = Down
+			preferredOppositeDir = Down // Edge goes to bottom of destination
 			alternativeDir = Left
 			alternativeOppositeDir = Down
 		} else {
-			preferredDir = Left
-			preferredOppositeDir = Down
+			// Backwards flow in TD mode - start from Right, arrive at Right
+			preferredDir = Right
+			preferredOppositeDir = Right // Edge goes to right of destination
 			alternativeDir = Up
 			alternativeOppositeDir = Right
 		}
 	default:
-		preferredDir = d
-		preferredOppositeDir = preferredDir.getOpposite()
-		// TODO: just return null and don't calculate alternative path
-		alternativeDir = d
-		alternativeOppositeDir = preferredOppositeDir
+		// Handle direct backwards flow cases
+		if isBackwards {
+			if graphDirection == "LR" && d == Left {
+				// Direct left flow in LR mode - start from Down, arrive at Down
+				preferredDir = Down
+				preferredOppositeDir = Down // Edge goes to bottom of destination
+				alternativeDir = Left
+				alternativeOppositeDir = Right
+			} else if graphDirection == "TD" && d == Up {
+				// Direct up flow in TD mode - start from Right, arrive at Right
+				preferredDir = Right
+				preferredOppositeDir = Right // Edge goes to right of destination
+				alternativeDir = Up
+				alternativeOppositeDir = Down
+			} else {
+				preferredDir = d
+				preferredOppositeDir = preferredDir.getOpposite()
+				alternativeDir = d
+				alternativeOppositeDir = preferredOppositeDir
+			}
+		} else {
+			preferredDir = d
+			preferredOppositeDir = preferredDir.getOpposite()
+			// TODO: just return null and don't calculate alternative path
+			alternativeDir = d
+			alternativeOppositeDir = preferredOppositeDir
+		}
 	}
 	return preferredDir, preferredOppositeDir, alternativeDir, alternativeOppositeDir
 }

cmd/testdata/ascii/back_reference_from_child.txt

@@ -3,8 +3,8 @@ A --> B --> C --> A
 ---
 +---+     +---+     +---+
 |   |     |   |     |   |
-| A |<-+->| B |--+->| C |
-|   |  |  |   |  |  |   |
-+---+  |  +---+  |  +---+
-       |         |       
-       +---------+       
+| A |---->| B |---->| C |
+|   |     |   |     |   |
++---+     +---+     +---+
+  ^                   |  
+  +-------------------+  

cmd/testdata/ascii/backlink_from_top.txt

@@ -7,16 +7,16 @@ D --> C
 ---
 +---+     +---+     +---+
 |   |     |   |     |   |
-| A |---->| B |---->| D |
-|   |     |   |     |   |
-+---+     +---+     +---+
-  |         |         |  
-  |         |         |  
-  |         |         |  
-  |         |         |  
-  |         v         |  
-  |       +---+       |  
-  |       |   |       |  
-  +------>| C |<------+  
+| A |---->| B |--+->| D |
+|   |     |   |  |  |   |
++---+     +---+  |  +---+
+  |         |    |       
+  |         |    |       
+  |         +----+       
+  |         |            
+  |         v            
+  |       +---+          
+  |       |   |          
+  +------>| C |          
           |   |          
           +---+          

cmd/testdata/extended-chars/back_reference_from_child.txt

@@ -3,8 +3,8 @@ A --> B --> C --> A
 ---
 ┌───┐     ┌───┐     ┌───┐
 │   │     │   │     │   │
-│ A ├◄─┬─►│ B ├──┬─►┤ C │
-│   │  │  │   │  │  │   │
-└───┘  │  └───┘  │  └───┘
-       │         │       
-       └─────────┘       
+│ A ├────►│ B ├────►│ C │
+│   │     │   │     │   │
+└───┘     └───┘     └─┬─┘
+  ▲                   │  
+  └───────────────────┘  

cmd/testdata/extended-chars/backlink_from_top.txt

@@ -7,16 +7,16 @@ D --> C
 ---
 ┌───┐     ┌───┐     ┌───┐
 │   │     │   │     │   │
-│ A ├────►│ B ├────►│ D │
-│   │     │   │     │   │
-└─┬─┘     └─┬─┘     └─┬─┘
-  │         │         │  
-  │         │         │  
-  │         │         │  
-  │         │         │  
-  │         ▼         │  
-  │       ┌───┐       │  
-  │       │   │       │  
-  └──────►│ C │◄──────┘  
+│ A ├────►│ B ├──┬─►┤ D │
+│   │     │   │  │  │   │
+└─┬─┘     └─┬─┘  │  └───┘
+  │         │    │       
+  │         │    │       
+  │         ├────┘       
+  │         │            
+  │         ▼            
+  │       ┌───┐          
+  │       │   │          
+  └──────►│ C │          
           │   │          
           └───┘